Was not expecting this but when I upgraded to Aperture 3 I discovered to my surprise that it needs to upgrade all your thumbnails in your library which in my case took over 5 hours to complete. I started upgrading at 1pm and did not see the new updated programme till 6.15pm…just over 5 hours later. I think Apple should give you some warning about this as this could be critical to some photographers not being able to use Aperture for such a length of time. In previous versions this was done under the hood….YOU HAVE BEEN WARNED…this is an overnight upgrade !